It has long been recognized in the ballistics field that slightly oversized projectiles engage the undersized bores of firearms through which they pass on firing and cause fouling. Firing frequently heats the bullet to the softening and perhaps the melting point and also heats the firearm barrel through which the projectile is fired. Microscopic surface defects or irregularities in the barrel increase frictional forces and remove minute metal particles from the projectile. These particles become imbedded on the inner bore surface of the firearm barrel.
Projectiles are generally manufactured of materials much softer, malleable and with a much lower melting point than barrel alloy. Upon being fired, the projectile will conform to the dimensions of the interior surface of the barrel. Typically firearm projectiles are made of cast/swaged lead bullets, jacketed bullets with a copper outer jacket and a soft lead core swaged into the copper jacket or, in the case of shot guns, pellet shot which is usually carried in a plastic "wad" or capsule.
The heat of powder and primer ignition and the heat of friction during the internal ballistic experience is tremendous for a few milliseconds. Barrel alloys get very hot and projectiles get so hot that they begin to soften, flow or melt on their trip down the barrel.
The rough, microscopic surface asperities of the bullet and barrel surfaces mutually abrade each other and minute particles of projectile surfaces are typically transferred by this abrasive action, heat and pressure from the projectile surface to the bore surface. In the early stages, the problem of this build-up on the bore surfaces from minute particles from the bullets is called "copper or lead wash". As the metallic build-up becomes more severe, such buildup is known as "copper, lead or plastic fouling".
It is well known that metallic fouling and foreign material in firearm barrels adversely affects firing accuracy. Metallic fouling irregularly alters the internal dimensions of the bore. Bullets passing over these irregularities, being altered by heat and pressure to conform to these irregularities, cause the bullets to become irregular and out of symmetry and thereby out of balance. This asymmetrical condition causes the bullet to yaw and wobble irregularly during flight from one shot to the next, and accuracy is diminished. Foreign debris of powder and primer residue, carbon, dirt and grit become abrasive and create irregular wear patterns on the relatively soft barrel alloy, similarly contributing to a decrease in accuracy.
This problem has been addressed with varying degrees of success by many inventors by using various lubricants including waxes, greases, soaps and dry lubricants applied to bullets and/or firearm bore surfaces. Oils and greases do not adhere well to the bullets or bore surfaces and may pick up abrasive dirt, dust and grit, or break down into acidic and corrosive agents. Under the extreme temperatures and pressures associated with firing they typically are burned off and do not add much lubrication or protection against corrosion. To the contrary, their waste products typically contribute further to the fouling problem.
Moreover, a safety hazard may be created with greases or oils in the barrel when these fluid lubricants are "snow plowed" ahead of a fired projectile as it travels down the firearm barrel. The resulting tremendous hydraulic pressure effects cause pressure excursions that will bulge or burst barrels and blow up the locking mechanism.
U.S. Pat. No. 4,858,534 to Wallace discloses the use of a lubricating composition comprising a polyolefin-base oil, amorphous silicon dioxide, and disodium octaborate tetrahydrate disposed in an indented ring around a bullet for lubricating firearm barrels through which such bullets are fired.
To avoid the use of oil- and grease-type lubricants, various solid lubricants have been suggested in the prior art. It is known, for example, among the elite of competition shooters that the use of 0.22 or 0.243 caliber bullets dry-coated with a lubricating layer of powdered molybdenum disulfide are effective in reducing the degree of metallic fouling to the extent that cleaning may not be required during a rifle match in which about 100 shots are fired. Normally, these small caliber bullets have a full metal jacket or hollow points with no lead exposed on the bullet nose. Typically these bullets are fired through expensive premium grade barrels on match rifles, the bores of which have been lapped and polished. These competitive shooters have noticed that the consistent use of powdered molybdenum disulfide coated bullets has extended barrel life.
Molybdenum disulfide is available as a dry powder of more or less 98-99 percent by weight molybdenum disulfide, generally three grades, ranging in average particle sizes from 2-63 microns. A typical product is available from Dow Corning Company, Midland Mich., as Dow Corning "Z Moly-Powder." Molybdenum disulfide has been applied as a dry powder lubricant to the sliding surfaces of metal equipment. FIG. 4 shows a magnified illustration of molybdenum disulfide particles, showing that the molybdenum disulfide particles consist of conglomerates of many small flakes which give the particles a gross appearance of being generally round or clam-shell shaped.
FIG. 5 illustrates the response of the molybdenum disulfide particles coated on a metal substrate when a steel ball slides over the surface onto which the molybdenum disulfide has been sprinkled. As shown therein, the particles are flattened and adhere very strongly to the underlying surface of the metal substrate.
FIG. 6 illustrates, that the mechanical stress induced by the ball has produced flat planes from the round grains, and wherein the lamella layers of the molybdenum disulfide of any given particle has been more or less shingled, thus to provide a thinner, plate-like particle having a larger surface area.
Thus, the "crushing" of the particles by the steel ball spreads the respective particles out over a greater portion of the underlying metal surface, with overlap of the respective thus enlarged particles, thus to make a quasi-layer comprising the overlapped particles, as illustrated in plan view in FIG. 7. FIG. 7 shows in enlarged cross-section, however, that the ovrlying layer of molybdenum disulfide does not fill the valleys lying between the peaks of the asperities on the substrate surface.
Thus, in dry-applied molybdenum disulfide, it appears that there is less, or poorer, bonding between particles than between lamella within a given particle, whereby the protective, metal conditioning layer is subject to being rubbed off the underlying metal surface which it is intended to protect.
It is clearly seen in FIG. 7 that the layer "a" of molybdenum disulfide touches the underlying surface only at peaks of the asperities of the underlying surface, and otherwise is generally spaced from the underlying surface at the valleys. Thus, the dry-coated layer of molybdenum disulfide provides interfacial contact with the underlying surface of the metal substrate only at the peaks, whereby the load/pressure between two metal surfaces so conditioned by such a layer is concentrated at the peaks, and is thus not spread out over the entire area of the underlying metal surface. Further, FIG. 7 shows major cracks "b" extending entirely through the thickness of the molybdenum disulfide layer "a," further illustrating the ability of the layer "a" to break up and flake off the metal surface.
While some success has been seen with the coating of smaller caliber target bullets with dry, powdered molybdenum disulfide, less success has been seen with the application of powdered molybdenum coating to larger bullets fired at greater velocities from higher powder capacity cartridges such as those employed in hunting-type bullets fired from mass production hunting rifles. Because of this limited success, the practice of using dry, powdered molybdenum disulfide to coat bullets is not widely accepted and is limited primarily to the competitive shooting fraternity. The reason for this lack of success in larger bullets is primarily due to the fact that with powdered molybdenum sulfide coating of bullets the maximum build of the coating is about 0.00005 inch (0.0013 mm). There is thus generally not enough molybdenum disulfide adhering to the bearing surface of the bullet to survive the transit in the rougher barrels of mass produced rifles. Thus, metallic fouling persists, in such applications requiring the regular and standard regimen of cleaning of the firearm barrel, typically with abrasive mechanical brushing and strong chemical solvents and/or polishing/cleaning compounds. The benefits to the hunter and non-competitive shooter are not great enough to justify the added cost of time and material of applying the powdered molybdenum disulfide.
Various methods have been suggested for applying a layer of dry powdered molybdenum disulfide to the surface of bullets which permits a more uniform and more adherent layer.
U.S. Pat. No. 4,454,175 Martin teaches a method of impact plating the surfaces of lead bullets with powdered molybdenum disulfide which comprises the steps of tumbling the bullets in a ball mill containing powdered molybdenum disulfide and steel shot. The process is applicable only to bullets and cannot be utilized for coating bullets in a fully loaded cartridge or for conditioning the inner bore of a firearm barrel. For the latter purpose, Martin, et al. teach in U.S. Pat. No. 5,378,499 the lapping of the bore of a firearm barrel by firing through it bullets which have been previously coated with an abrasive such as diamond powder, boron nitride, boron carbide, silicon carbide, and the like.
To overcome the drawbacks associated with coating bullets with dry, powdered molybdenum disulfide, various methods have been suggested in the prior art which employ liquid compositions comprising molybdenum disulfide.
U.S. Pat. No. 4,196,670 to Vatsvog, for example, teaches a process for uniformly coating bullets with molybdenum disulfide lubricant by spray or dip coating the bullets with a suspension of molybdenum disulfide in an epoxy phenolic resin. The patentee teaches that the wet-coated bullets are then allowed to air dry. For an effective and rapid cure of epoxy phenolic resins, however, the resin coating should be heat cured. If the coating is allowed to air dry as taught by the patentee, this process suffers from the disadvantage of requiring long cure times before the coating is ready for its intended use.
U.S. Pat. No. 5,062,974 to Van Meter discloses a surface treatment for firearms and bullets comprising finely divided molybdenum disulfide, an alkali metal molybdate and a volatile organic solvent such as trichloroethane. The patentee teaches that the sodium molybdate adheres to the underlying metal substrate, with the molybdenum disulfide adhering to the sodium molydate.
The methods taught in the prior art for coating firearm projectiles or conditioning the inner bore of a firearm barrel, however, do not adequately address the problem of how to effectively and conveniently apply molybdenum disulfide to bullets, and to condition firearm bores and reloading components to remedy these conditions of fouling, cleaning, corrosion, and erosion in a cost effective way.
Thus it is one object of the present invention to provide compositions and methods for applying a desired amount of a bonded molybdenum disulfide composition as a coating to bullets and firearm components.
It is another object of the invention to provide compositions and methods for applying a desired amount of a molybdenum disulfide composition as a bonded coating on other ballistics apparatuses such as gun barrels, firearm chambers, fully assembled cartridges, shotgun wads, shot capsules and sabots.
It is yet a further object of the invention to provide compositions and methods that effectively degrease the surface of the substrate material to be coated in preparation for the process of applying the molybdenum disulfide coating, such that the degreasing and coating are performed in a single step of applying coating material while preparing that substrate material surface for coating.
It is a further object of the invention to provide compositions and methods that readily, easily, cost effectively harden the interior barrel alloy surfaces of a firearm such that erosion of the barrel surface is minimized and that the useful life of the barrel is greatly extended.
It is yet another object of the invention to smooth the interior surface of the barrel to eliminate or minimize fissures, pitting, ruptures of the alloy surface.
It is another object of the invention to provide compositions and methods that readily, easily, cost effective repairs, heals, mends and restores to a considerable extent the fissured, eroded, degraded surfaces of used firearms.
It is also another object of the invention to provide compositions and methods that readily, easily, cost effectively protect the interior and exterior surface alloy of firearms from corrosive elements such as water, salt water, powder and primer corrosive by-products, environmental acids and solvents.
It is also another object of the invention to provide an environmentally safe protective coating to lead and other metallic shot such that will not degrade to produce lead products in environmental wetlands and in the digestive tracts of waterfowl.
It is also another object of the invention to provide a surface buffering zone to exterior surfaces of metallic bullet components to prevent oxidation, corrosion, etc. by applying MOS.sub.2 to the product surfaces before, during and after steps in the manufacture of swaged lead wire and molded lead bullets, bullet molds, sheet copper, copper billets, copper wire, in jacketed bullets, to molded/extruded plastics in shot wads, and ferrous alloys in firearm barrels, actions, and other components.
It is the final object of the invention to provide compositions and methods that readily, easily, and cost effectively minimizes or eliminates the frequent need for a cleaning process to remove metallic fouling, carbon and powder residue fouling and corrosion in firearms.